A Full-Length Quench Antenna Array for MQXFA Production Series Quadrupole Magnet Testing

The MQXFA production series quadrupoles being built for the Hi-Lumi (HL) LHC upgrade by the US Accelerator Upgrade Project (US-HL-LHC AUP) will have very limited voltage instrumentation for characterizing quench events that occur during magnet training and performance validation testing. In order to understand the origin of the quenches, and whether they have some implication for ongoing magnet fabrication, a full-length Quench Antenna Array (QAA) was built with axial resolution of 50 mm to be employed during cold testing in the anti-cryostat. The goal is to have fine-resolution, full-length coverage detection of quench events axially, as well as to have azimuthal resolution on the order of the cable width (about 1 degree for the cross-section), in a device that can be used both for vertical and horizontal testing. To achieve this, a 5 m long QAA with 128 channels of high-speed data acquisition has been designed and fabricated. The array features full-length radially positioned antennas for azimuthal localization, and short, high-sensitivity, antennas for axial detection. This paper discusses the design, construction and analysis of the MQXFA QAA, and first results from its use during quench testing in the production magnets.